Split Gaussia Luciferase for Imaging LigandReceptor Binding

Ligand binding to cell surface receptors activates signaling pathways in normal and pathologic conditions, and internalized ligand–receptor complexes may continue to signal from endosomes. Accessibility of cell surface receptors and the central function of ligand–receptor binding in signal transduction make ligand binding a prime target for therapeutic agents. We describe a Gaussia luciferase complementation method for imaging ligand–receptor binding in cell-based assays and living mice. While we illustrate this imaging method for chemokine ligand CXCL12 and its receptors CXCR4 and CXCR7, this imaging strategy can be generalized to a large number of ligand–receptor interactions.